They've shared many flirtatious and playful interactions over the years, including perpetuating false rumours they'd shared a child together.
And on Monday, Russell Brand professed his grand admiration of Australian journalist and radio host Fifi Box while on The Project.
The outlandish comedian, 42, announced Fifi was his 'third favourite Australian.'
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'She's my third favourite Austrlaian!' Russell Brand unashamedly gushes over radio host Fifi Box... after flirtaceously suggesting he fathered her five-year-old daughter Trixie
Russell compared the mother-of-one to Australian bushranger Ned Kelly and Australian tennis player Rod Laver.
The actor brought up the blonde after host Peter Helliar claimed their serious discussion on Russell's life and fourth book, Recovery: Freedom From Our Addictions, was far more mature than their last encounter.
'Last time I came on your show it was a mental, crazy laugh. And this time it seems we're talking a bit more spiritually and a bit more maturely,' Russell said.
'Russell, I do blame last time you were on, our lack of maturity on Fifi Box, just so you know,' Peter said.
Russell laughed as he responded: 'So do I. In the absence of Fifi, we're talking about the nature of reality. When Fifi is present, we squirt out a fecal-looking moose on to the desk.'
'Historically! Really covering an expanse': Russell placed the mother-of-one behind Australian bushranger Ned Kelly and Australian tennis player Rod Laver in his top-three favourite Australians of all time
'You really seem to spread your favourite Australians out,' Peter exclaimed, with Russell cheekily agreeing: 'Historically! Really covering an expanse.'
When ending the interview with the Hollywood star, host Carrie Bickmore said: 'It's been an absolute pleasure, as always. We'll say hi to Fifi Box for you.'
Russell waved and thanked the panel, while asking them to 'give her (Fifi Box) my love!'
'Give her (Fifi Box) my love!' Russell mentioned Fifi Box three times during his interview, despite the blonde media personality being absent from the desk
Their playful chemistry was taken to the next level when he joked that he was the father of Fifi's daughter Beatrix 'Trixie' Belle, in 2015.
And while she was vehement in her denial, it seems Russell wasn't about to let the point go.
Returning to The Project, where he first made the outlandish claims in June that year, the comedian flirted up a storm with the radio host, and at one point humorously suggested he would be keen to try for a sibling for her then two-year-old.
What a flirt! Russell Brand couldn't help but flirt up a storm with Fifi Box on Friday's The Project after joking earlier this year that he had fathered her daughter Trixie
While explaining how he gets into the